Development of binary superconducting current leads with a gas cooled normal part

The design of a binary superconducting 1 kA current lead, operating between 300 K and 4.2 K, will be presented. The normal conducting part of the lead, will be cooled by high pressure helium gas of 60 K inlet temperature. The resulting warm end temperature of the conduction cooled high-temperature superconductor (HTSC) part is about 67 K and as a consequence a magnetic stray field of 0.2 T can be tolerated, A total heat load of 0.2 W at 4.2 K has been foreseen. The required room temperature power input of the refrigerator is reduced to about 25 % as compared to an optimised conventional current lead.